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TARTARIC ACID

2.  Fixed Residue.—2 grams are cautiously calcined in a platinum
dish and any residue examined in the usual way.

3.  Sulphuric Acid.—The I : 10 solution is tested with barium chloride.

4.  Oxalic Acid.__The I : 10 solution, neutralised with ammonia, is

treated with calcium sulphate.

5.  Lime.__The I : 10 solution is rendered alkaline with ammonia and

tested with ammonium oxalate.

6.  Heavy Metals.—The i : 10 solution is treated with hydrogen sulphide,
or neutralised with ammonia and then treated with ammonium sulphide.

7.  Arsenic.—The concentrated solution should not  be coloured by
Bettendorf's reagent.

8.  Quantitative Determination.—In absence   of other   free acids,
the aqueous solution of the acid is titrated with N-alkali in presence of
phenolphthalein :   i c.c. N-alkali = 0-07502 gram of tartarie acid.

The pure acid should leave no weighablc residue : the Italian Pharmacopoeia
allows 5 parts per 1000. The commercial acid often contains lead partly com-
bined and partly free ; as much as cvu gram per kilo has been round.

Tartars and other Tartarie Substances

These are. mainly wine- /ecu, cask incrustation, crude tartars and cnulc>
calcium tartratc.

Wine, lees consist of a slimy, reddish mass containing essentially yeasts,
cream of tartar, calcium tartratc, colouring matter and water. Cask
incrustations and crude tartars are composed of dirty white, or reddish crys-
talline crusts or masses. Crude calcium larlmie is a. greyish or reddish
powder almost.insoluble in water but soluble in dilute acids.

For the analysis of these! substances a homogeneous sample must be
prepared ; the substance is well mixed and powdered so that it passes
through at least a | millimetre sieve.

In all the products it is necessary to determine the tartu.ric acid, whether
combined with potash or lime. According to the methods adopted at the
Seventh International Congress of Applied Chemistry, London, i()<>(), the
tartarie acid is determined as follows :

1.  Determination of the Tartarie Acid existing as Potassium
Bitartrate.—2-350 grams of the, substance, are boiled, for 5 minutes with
about 400 c.c. of water in a 500 c.c. flask, a further quantity of water being
added and the. whole allowed to cool, made up to volume, mixed and filtered
through a pleated filter.    Of the filtrate 250 c.c. (-•• 1-175 gram of substance)
are heated to boiling and titrated with N/4-caustie alkali standardised by
means of bitartrate (puriss.), using sensitive litmus paper (phenolphthalein
may also conveniently be used).

2.  Determination  of the  Total  Tartarie  Acid   (Goklenberg and
G&omont's method, modified) .—6 grams (12, if poor in tartarie acid) of
material are weighed and, together with 18 c.c. of HC1 (I) i-io), introduced
into a 150-200 c.c. beaker.   The whole is thoroughly mixed and stirred at
the ordinary temperature, the lumps being broken with a glass rod and the
particles washed from the sides of the beaker with small quantities of water
from a wash-bottle.   After digestion for 10-15 minutes, the whole is washed